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Fix for deadlock situation in cuse(3)

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The final server unref should be done by the server thread to prevent
deadlock in the client cdevpriv destructor, which cannot destroy
itself.

MFC after:	1 week
Sponsored by:	Mellanox Technologies
This commit is contained in:
Hans Petter Selasky 2019-06-25 11:42:53 +00:00
parent 019c8c9330
commit c7ffaed92e
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=349367
1 changed files with 29 additions and 14 deletions
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43
sys/fs/cuse/cuse.c
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@ -699,12 +699,38 @@ cuse_server_unref(struct cuse_server *pcs)
free(pcs, M_CUSE);
}
static int
cuse_server_do_close(struct cuse_server *pcs)
{
int retval;
cuse_lock();
cuse_server_is_closing(pcs);
/* final client wakeup, if any */
cuse_server_wakeup_all_client_locked(pcs);
knlist_clear(&pcs->selinfo.si_note, 1);
retval = pcs->refs;
cuse_unlock();
return (retval);
}
static void
cuse_server_free(void *arg)
{
struct cuse_server *pcs = arg;
/* drop refcount */
/*
* The final server unref should be done by the server thread
* to prevent deadlock in the client cdevpriv destructor,
* which cannot destroy itself.
*/
while (cuse_server_do_close(pcs) != 1)
pause("W", hz);
/* drop final refcount */
cuse_server_unref(pcs);
}
@ -746,21 +772,10 @@ static int
cuse_server_close(struct cdev *dev, int fflag, int devtype, struct thread *td)
{
struct cuse_server *pcs;
int error;
error = cuse_server_get(&pcs);
if (error != 0)
goto done;
if (cuse_server_get(&pcs) == 0)
cuse_server_do_close(pcs);
cuse_lock();
cuse_server_is_closing(pcs);
/* final client wakeup, if any */
cuse_server_wakeup_all_client_locked(pcs);
knlist_clear(&pcs->selinfo.si_note, 1);
cuse_unlock();
done:
return (0);
}